2 Answers

I doubt the computer is the issue. For all of the broken down junk I have worked on over 30 years any many different brands I have never seen a computer fail. I am not an expert on German vehicles but engines will all run the same way.
All engines need air, all engines need fuel, all engines need a spark to ignite the fuel unless it is diesel.(that is compression) You did not tell us if your Jetta was gasoline or diesel. Did you squirt some fuel into the throttle body and see if it runs? If if does start up and run for a few seconds then you have bad fuel pump.

often the reason for a jetta this old to stop running is often either a clogged gas filter, A carbon built up MAF, or the coil pack or spark plugs have gone bad. These are the most common reasons your car would just not start. The other reasons would be if you have the 2.8L engine there is a vacuum line that tends to break off due to the heat of the engine. normally located down around where the oil fill slot is. Other reasons are blocked or clogged crank case hoses which will happen over a long period of time. To check the crank case hoses remove your engine cover and look for a plastic hose with a plastic spreader cap attached to head cover and pull it off. If there is a large amount of sludge in there have them all replaced. You can find them online relatively cheap and it comes with all the breather hoses and connectors as well as the vacuum container. Try checking all these things then get back to us with more info.

My jetta 2001 2.0 had a lot of problems in the last couple of months and I took it to the mechanic and he said that I have to change the computer but I need to know where in the car it is so I can go ...